View source for 7cr6


==Synechocystis Cas1-Cas2/prespacer binary complex==
<StructureSection load='7cr6' size='340' side='right'caption='[[7cr6]], [[Resolution|resolution]] 3.72&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[7cr6]] is a 8 chain structure with sequence from [https://en.wikipedia.org/wiki/Synechocystis_sp._PCC_6803_substr._Kazusa Synechocystis sp. PCC 6803 substr. Kazusa] and [https://en.wikipedia.org/wiki/Synthetic_construct Synthetic construct]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=7CR6 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=7CR6 FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 3.72&#8491;</td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=7cr6 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=7cr6 OCA], [https://pdbe.org/7cr6 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=7cr6 RCSB], [https://www.ebi.ac.uk/pdbsum/7cr6 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=7cr6 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/Q6ZEI2_SYNY3 Q6ZEI2_SYNY3] CRISPR (clustered regularly interspaced short palindromic repeat), is an adaptive immune system that provides protection against mobile genetic elements (viruses, transposable elements and conjugative plasmids). CRISPR clusters contain spacers, sequences complementary to antecedent mobile elements, and target invading nucleic acids. CRISPR clusters are transcribed and processed into CRISPR RNA (crRNA). Acts as a dsDNA endonuclease. Involved in the integration of spacer DNA into the CRISPR cassette.[HAMAP-Rule:MF_01470]
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== Publication Abstract from PubMed ==
CRISPR-Cas immune systems process and integrate short fragments of DNA from new invaders as spacers into the host CRISPR locus to establish molecular memory of prior infection, which is also known as adaptation in the field. Some CRISPR-Cas systems rely on Cas1 and Cas2 to complete the adaptation process, which has been characterized in a few systems. In contrast, many other CRISPR-Cas systems require an additional factor of Cas4 for efficient adaptation, the mechanism of which remains less understood. Here we present biochemical reconstitution of the Synechocystis sp. PCC6803 type I-D adaptation system, X-ray crystal structures of Cas1-Cas2-prespacer complexes, and negative stained electron microscopy structure of the Cas4-Cas1 complex. Cas4 and Cas2 compete with each other to interact with Cas1. In the absence of prespacer, Cas4 but not Cas2 assembles with Cas1 into a very stable complex for processing the prespacer. Strikingly, the Cas1-prespacer complex develops a higher binding affinity toward Cas2 to form the Cas1-Cas2-prespacer ternary complex for integration. Together, we show a two-step sequential assembly mechanism for the type I-D adaptation module of Synechocystis, in which Cas4-Cas1 and Cas1-Cas2 function as two exclusive complexes for prespacer processing, capture, and integration.

Mechanisms of spacer acquisition by sequential assembly of the adaptation module in Synechocystis.,Wu C, Tang D, Cheng J, Hu D, Yang Z, Ma X, He H, Yao S, Fu TM, Yu Y, Chen Q Nucleic Acids Res. 2021 Mar 18;49(5):2973-2984. doi: 10.1093/nar/gkab105. PMID:33619565<ref>PMID:33619565</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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<div class="pdbe-citations 7cr6" style="background-color:#fffaf0;"></div>

==See Also==
*[[Endonuclease 3D structures|Endonuclease 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Synechocystis sp. PCC 6803 substr. Kazusa]]
[[Category: Synthetic construct]]
[[Category: Chen Q]]
[[Category: Yu Y]]